The present invention relates to a carrying apparatus and an image forming apparatus which are contained in, for example, an electrophotographic copying machine carrying paper sheets.
In some electrophotographic copying machines, images can be formed on both surfaces of a paper sheet. When images are formed on both surfaces of a paper sheet in these electrophotographic copying machines, paper sheets are fed from a sheet feed cassette through a sheet carrying route to an image forming section (hereinafter called simply an ADU). An image is formed on one surface of the paper sheet, and the image is then heated by a fixing device, to fix it to the paper sheet. The paper sheet having the image fixed to its surface is once stacked and contained into an intermediate tray. Subsequently, the paper sheet thus stacked and contained in the intermediate tray is fed again to the image forming section, and an image is transferred to its back surface. In this manner, images are formed on both surfaces of the paper sheet which is then discharged onto a sheet discharge tray.
Meanwhile, paper sheets stacked on the intermediate tray are applied with static electricity. Therefore, fed paper sheets easily tend to be stuck to each other when the paper sheets are fed again from the intermediate tray.
In addition, since a paper sheet having a surface on which an image has been formed must once be stacked and contained in the intermediate tray, image formation cannot be performed sequentially on its back surface. Time loss is hence caused so that the image forming efficiency is lowered.
To solve the above-described problems of fed paper sheets being stuck to each other and the image forming efficiency being lowered, development has been made in an electrophotographic copying machine which adopts a so-called non-stack ADU.
That is, in this electrophotographic copying machine, the intermediate tray is excluded from the ADU. Images are formed sequentially on the surfaces of a plurality of paper sheets. Further, these paper sheets are sequentially reversed by a reverse carrying means, and are directly sent to the image forming section. Images are formed on the back surfaces of the paper sheets.
In some cases, the non-stack ADU is used with an accounting device such as a coin controller attached to the ADU. If a total of 4 pages are double-side-printed on two paper sheets in an electrophotographic copying machine attached with the accounting device, for example, there may be a case that the inserted money runs short at the time point when printing on pages 1, 2, and 4 pages is finished.
In this case, the paper sheet on which the third page should be printed is discharged without carrying out printing, or is kept on the ADU in the apparatus.
It is, however, unkind to users to discharge the paper sheets without completing the printing process.
On the other hand, if a paper sheet is kept on the ADU, it may be stopped at the fixing device. If it is positioned at the fixing device, the paper sheet may be burnt, emit smoke, or catch fire due to the fixing device.
If the heat source of the fixing device is turned off when a paper sheet is kept, the paper sheet does not burn, smoke, or catch fire. However, in order to turn off the fixing device to pause carrying of the paper sheet during printing operation, the fixing device must be heated again at the time of restarting the printing operation. The processing efficiency is undesirably deteriorated.
The present invention has been made in view of the situation described above and has an object of providing a carrying apparatus and an image forming apparatus in which an object to be carried (to which an image should be transferred) is not positioned at the fixing device when the object is temporarily kept.
A carrying apparatus according to the present invention comprises: a carrying device for carrying an object to be carried, along a carrying route; a heating device for heating the object being carried along the carrying route; a control device for temporarily stopping and keeping the object being carried along the carrying route, if necessary; and a detection device for detecting whether the object is positioned at the heating device, when carrying of the object is temporarily stopped by the control device, wherein if the detection device detects the object positioned at the heating device, the control device controls operation of the carrying device so as to carry the object until the detection device does not detect the object any more, and then to stop carrying of the object.
An image forming apparatus according to the present invention comprises: an image forming device for forming an image on an image carrier; a transfer device for transferring the image formed by the image forming device, to one surface of an object to which an image should be transferred; a fixing device for heating the image transferred by the transfer device, thereby to fix the image to the object; a carrying device for carrying the object along a main carrying route, thereby to feed the object through the image forming device, the transfer device, and the fixing device; a reverse carrying device for carrying the object with the image fixed to the one surface, along a reverse carrying route, thereby to reverse and feed the object again to the transfer device, so as to transfer an image to another surface of the object; a control device for temporarily stopping and keeping the object being carried along the main or reverse carrying route, if necessary; and a detection device for detecting whether the object is positioned at the fixing device, when carrying of the object is temporarily stopped by the control device, wherein if the detection device detects the object positioned at the fixing device, the control device controls operation of the carrying device so as to carry the object until the detection device does not detect the object any more, and then to stop carrying the object.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.